U.S. Pat. No. 2,333,614 (Boyd) discloses a pump system having air-compressing cups that are secured in an inverted orientation to metallic plates anchored in the pavement. Movement of a vehicle across the cup causes the cup to collapse, forcing air from the cup into a compressed air storage tank, which can then be used to perform useful work.
U.S. Pat. No. 4,004,422 (Le Van) discloses a method and apparatus for producing useful work by utilizing the weight of moving traffic by incorporating in a roadway or traffic-way a readily deformable chamber which is filled with a fluid arranged so that the weight of a vehicle in passing thereof affects a displacement of the fluid therein. The energy of the displaced fluid in turn is translated into mechanical or electrical energy.
U.S. Pat. No. 4,322,673 (Dukess) discloses an energy conservation and highway safety apparatus for supplying supplemental or emergency electrical power caused by passage of vehicles over the apparatus comprising a plurality of elongated conduits having a plurality of pressure responsive pumping elements mounted therein. The conduits are connected through an accumulator to an air motor which drives a generator.